GB2240660A

GB2240660A - Vacuum switch

Info

Publication number: GB2240660A
Application number: GB9102240A
Authority: GB
Inventors: Wilhelm Schels; Manfred Niegl
Original assignee: Sachsenwerk Licht und Kraft AG; Sachsenwerk AG
Current assignee: Schneider Electric Sachsenwerk GmbH; VEM Sachsenwerk GmbH
Priority date: 1990-02-01
Filing date: 1991-02-01
Publication date: 1991-08-07
Anticipated expiration: 2011-02-01
Also published as: GB2240660B; JPH04349320A; DE4002933A1; GB9102240D0; US5099093A; DE4002933C2

Abstract

A vacuum switch has two similar, mutually opposed switch contacts each of which is provided with a pot-shaped winding body (5) with an annular contact element (10) mounted on the open end face of the body (5). The winding body (5) is traversed, in order to form winding conductors, by a number of slits (6) which are inclined in relation to the axis of a contact stud carrying the contact and which are distributed symmetrically over the periphery. The slits (6) which may be four in number are inclined at an angle of 60 DEG to 75 DEG in relation to the axis of the contact studs and in a region between the contact element (10) and the base of the pot-shaped body (5), extend over an angle of rotation of not more than 60 DEG to 90 DEG . The annular contact (10) is defined by a number of sectors, one for each winding conductor. Each contact sector (10) has at least one incision (11) extending in the radial direction from the inside towards the outside. A supporting ring is positioned contiguous to the internal diameter of the wall of the body (5). The radial wall thickness of a winding conductor is equal to about 10% of the external diameter of the body (5). <IMAGE>

Description

VACUUM SWITCH CHAMBER ASSEMBLY The invention relates to a vacuum switch

chamber assembly comprising two similar switch contacts which are situated opposite each other, which are positioned on mutually facing end faces of coaxial contact studs and which each have a pot-shaped winding body on the open end face of which is mounted an annular contact element, the wall of the pot being traversed, in order to form winding conductors, by a number of slits which pass the whole way through the base of the pot and which are inclined in relation to the axis of the contact studs and which are evenly distributed over the periphery, as well as with a concentric supporting ring in the hollow space between the base of the winding body and the contact element, the contact element consisting of annular sectors each of which extends in the peripheral direction over that section of a winding conductor which is included between two slits.

A known assembly of this kind (DE-OS 32 27 482) has two switch contacts of identical construction, each positioned on an end face of coaxial contact studs and situated opposite each other. The switch contacts in this case each consist of a pot-shaped winding body on the open end face of which is mounted a contact element having the general shape of a circular or annular plate. When the switch contacts are closed the contact elements rest flat against one another. The walls of the pot- shaped structure of the winding body are traversed by a number of slits in order to form winding conductors serving to generate an axial magnetic field, these slits also passing through the base of the pot. The slits are inclined at a considerable angle in relation to the axis of the contact studs and are distributed symmetrically over the periphery of the winding body. inside the hollow space between the floor of the winding body and the contact

2 - element is a concentric supporting ring, situated in that zone of the contact element which is in the vicinity of the axis. The contact element has radial slits continuing in the respective associated slits of the wall of the pot-shaped winding body.

The object of the invention is to improve a vacuum switch of the type initially mentioned by ensuring a high degree of arc-back safety when switching off a high short-circuit current with a high short-circuit alternating current value.

In accordance with the invention, this is achieved in an arrangement as referred to, wherein preferably four slits in each case are formed by plane cuts through the wall of the pot-shaped body which are inclined at an angle of between 600 and 750 in relation to the axis of the contact studs, the arrangement being such that the middle surface of these cuts, in the zone of the wall of the pot, sweeps through an angle of rotation of not more than 600 - 900 in the peripheral direction and that each annular sector has at least one incision which extends in the radial direction from the inside towards the outside and as f ar as the zone of the internal diameter of the wall of the pot-shaped winding body, the radial wall thickness of a winding conductor being equal to about 10% of the external diameter of the winding body.

in one version of a vacuum switch according to the invention a section of each winding conductor, measuring only one slit-width less than 900 of the periphery, is taken directly to the rear of an annular sector of the contact element, in the zone of its external diameter, and conductively connected with the said element. This serves to ensure the maximum possible axial magnetic - R - flux up to diameters as close as possible to the external diameter of the contact element. With an external dia meter of 10Omm the short circuit current may amount to at least 40 KA and the nominal voltage to at least 36 kv. It has nevertheless been found, in measurements of the magnetic field of the switch contacts, that while the arc is alight the only flow filaments possible in the annular sectors of the contact elements are those which f rom the base points of the arc take a course sub stantially radial to the relevant section of the winding conductor. A -particular contribution is made to this object by the incisions made from the inside towards the outside, which only extend as far as the internal diameter of the winding conductor. The axial magnetic field generated in the winding conductors when current flows across the arc remains practically uninfluenced by the magnetic field occurring as a result of the radial flow filaments in the annular sectors. As the flow filaments are prevented from taking any other directions in the contact elements, the axial magnetic field is not weakened by such flow filaments in the contact plate even if the base joints of the arc are unevenly distributed on the surface of the contact, on the contrary, the axial magnetic field, in places corresponding to uneven agglom erations of the base points of the arc on the surf ace of the contact, is actually intensified on the contact element in question by a corresponding increase in pro portion of current flowing through winding conductors with which the annular sectors are associated and on which the agglomeration of base points occurs. Because of the additional incisions the eddy currents occurring in the annular segments are now practically all of neglible magnitude.

The slits provided for the formation of the winding conductors in the switch contacts also subdivide the base of the pot-shaped winding body so that undesirable eddy currents are prevented here as well. Furthermore, no agglomerations of base points of the arc can form in the zone of the axis of the contact, because the annular sectors terminate at a distance from the said axis or from that of the contact stud.

As each contact is, in the preferred case, provided with four slits at a greater inclination in relation to the axis of the contact studs, f lat sections of the winding are created which take a greater axial proportion of the magnetic f ield. In contrast, the magnetic fields resulting from eddy currents are negligible in their magnitude. The system is so arranged that the slits in the wall of the pot-shaped winding body extend over an angle of rotation of not more than 900 in the peripheral direction and then continue at the same angle of inclination through the base of the pot. In addition, the switch contacts are provided, between the contact element and the base of the pot, with a thin-walled supporting ring still very close to the internal diameter of the wall of the pot and made of CrNi steel of low electrical conductivity, this ring protecting the sections of the coil from the impact forces occurring when the contact elements are pressed together. Its position close to the winding conductors reduces to a minimum the effect of the bridging of the winding conductors.

The annular sectors may be interconnected in the zone of the external diameter, preferably by a thin crosspiece. This facilitates the operation of soldering them to the winding body.

To simplify the process of securing the supporting ring it is soldered radially, on the open side of the pot of the winding body, to the internal wall of the said pot. For this purpose it is provided, on its marginal zone facing towards the contact sectors, with a soldering collar directed radially outwards.

Other advantageous embodiments are indicated in the further claims.

of the invention The invention will be explained below by reference to the drawing of an example thereof.

in detail The diagrams are as follows:

Fig. 1:

A general diagram of a sectioned vacuum switch chamber, with switch contacts.

Fig. 2:

A side view of a switch contact.

Fig.3: An illustration of a switch contact in perspective.

Fig. 4: A side view of the winding body of a switch contact.

Fig.5: An illustration, in perspective, of a winding body according to Fig.4.

A vacuum switch chamber is provided, inside an evacuated housing I, with two switch contacts 2 facing each other by their faces, which latter are fitted with contact elements. The switch contacts 2 are mounted on the mutually facing end faces of coaxial contact studs 4, at least one of which is secured in an axially movable manner. In the vicinity of the contact elements 3 the switch contacts are provided with a pot-shaped winding body 5 on the exposed end f ace of which are mounted the contact elements 3. The walls of the pot-shaped winding body 5, which form the casing, are subdivided by four slits 6 into four winding conductors 7. The middle portion of the slits 6 is produced by plane cuts which are made through the wall of the pot and which are inclined by an angle of between 650 and 700 in relation to the axis of the contact studs, which is indicated at 8. The middle surface of these cuts in the zone of the wall of the pot, i.e. between the base surface 9 of the pot and the edge 50 providing the transition from the said middle portion of the slit 6 to the portion of which the plane includes the axi. of the contact, sweeps through a rotation angle of between 600 and 900 in the peripheral direction.

The contact elements 3 each consist of four annular sectors 10 which are each associated with a winding conductor 7 and which extend over the peripheral portion of the latter on the open side of the winding body. The radial distance of the internal edges of the annular sectors 10 from the axis 8 is equal to at least 35% of the external radius of the winding body 5. Each annular sector 10 has at least one incision and in the present case two incisions 11 extending in the radial direction from the inside to the outside, which extend as far as the internal diameter and preferably even to a slight distance into the zone of the winding conductor 7 in questions.

The slits 6 extend on the one hand also through the base 51 of the pot and in the radial direction are cut to a depth exceeding the thickness reached in the radial direction by the wall of the coil sections. The depth to which the slits 6 are cut in the base 51 of the pot, as measured from the external diameter of the winding body 5, is equivalent to about 40% of the diameter of the winding body 5. This construction counteracts the formation of undesirable eddy currents. In the zone i of the annular sectors 10 the slits 6 take their course between adjacent annular sectors 10 in a plane containing the axis 8 of the contact studs 4.

In the hollow space between the annular segments 10 and the base 51 of the pot a supporting ring 12 is provided which is concentric with the axis 8, rests on the base 5 of the pot and on the other hand supports the winding conductor sections in the vicinity of the open side of the pot. On the outer periphery the annular sectors 10 are vertically offset in the manner of a step 13 in the direction of the winding body, while f rom a plane central section they are radially bevelled towards the inside. This toroidal design for parts 15 of the surface whichface towards the axis serves to ensure an even distribution of the base points of the arc ont he contact surface. On the other hand, the step 13 directed radially outwards limits the contact transition zone of the operating current, and thus the zone of the contact element on which the first base points of the arc occur immediately after the galvanic separation of the contacts, to a diameter range having a high axial magnetic flux density. The supporting body 12 is thus situated in the middle part underneath the plane section of the annular sectors 10, which are subjected to the impact of the forces acting on the closing of the contacts 2. These forces are thus transferred directly to the base 15 of the pot and cannot cause any narrowing of the slits 6 or lead to any mechanical vibrations in the winding body. in addition, the supporting ring 12, because of its proximity to the highly conductive winding conductors 7, represents no appreciable shunt path for cross currents or eddy currents. As a simple securing means for the supporting ring 12 a soldering collar 14 is provided, shaped onto that marginal zone of the supporting body 12 which faces towards the winding body and projecting radially outwards. The supporting ring is thus secured by the soldering in the same way as on the base 51 of the pot. The slits 6 in the contact elements 3 of the two switch contacts 2 can be positioned congruently with each other in the vacuum switch chamber. They may also be rotated to a different angle to each other about the axis 8, the mutual angular position to which they are rotated being preferably 450.

The annular sectors 10 also consist of a sinter metal with up to 75 parts of copper and 25 parts of Chromium in accordance with DE-PS 34 06 535.

A vacuum switch chamber in accordance with the foregoing description, given a maximum contact distance of 20 mm and an external switch contact diameter of 98 mm, for a short circuit current with a short circuit alternating current value of 40 KA with a nominal voltage of 36KV or a short circuit alternating current value of 50 KA with a nominal voltage of 24 KV and 50 Hz, meets the requirements given in the relevant regulations, as regards switching capacity with higher arc-back safety. The radial width of the winding conductors 7 amounts to about one tenth of the diameter of the winding body 5, while the wall thickness of the supporting ring 12 is equal to about one quarter of that of a winding conductor 7.

Claims

1. A vacuum switch chamber assembly comprising two similar switch contacts which are situated opposite each other, which are positioned on mutually facing end faces of coaxial contact studs and which each have a pot-shaped winding body on the open end f ace of which is mounted an annular contact element, the wall of the pot being traversed, in order to form winding conductors, by a number of slits which pass the whole way through the base of the pot and which are inclined in relation to the axis of the contact studs and which are evenly distributed over the periphery, as well as with a concentric supporting ring in the hollow space between the base of the winding body and the contact element, the contact element consisting of annular sectors each of which extends in the peripheral direction over that section of a winding conductor which is included between two slits, wherein preferably four slits in each case are formed by plane cuts through the wall of the pot-shaped body which are inclined at an angle of between 600 and 750 in relation to the axis of the contact studs, the arrangement being such that the middle surface of these cuts, in the zone of the wall of the pot, sweeps through an angle of rotation of not more than 600 - 900 in the peripheral direction and that each annular sector has at least one incision which extends in the radial direction from the inside towards the outside and as far as the zone of the internal diameter of the wall of the pot-shaped winding body, the radial wall thickness of a winding conductor being equal to about 10% of the external diameter of the winding body.

2. An assembly in accordance with Claim 1, wherein that part of the slit which is situated between adjacent annular sectors takes its course in a plane which include the axis of the contact studs.

3. An assembly in accordance with Claim 1 or 2, wherein that part of the slit which takes its course in the plane of the axis of the contact studs extends into that end face of the winding body which is adjacent to the annular sectors.

4. An assembly in accordance with any preceding Claim, wherein that marginal zone of the supporting ring which faces towards the annular sectors has a soldering collar which extends radially outward in the direction of the winding sections- and which is of limited radial and axial height and to which the winding sections are soldered.

5. An assembly in accordance with any preceding Claim wherein the external radius of the annular sectors is smaller than the external radius of the winding body and that an annular recess passing the whole way round is shaped into the end f ace of the winding body and is flatter than the axial height of the annular sectors, the annular sectors being secured in the said recess.

6. An assembly in accordance with any preceding Claim wherein adjacent annular sectors are interconnected, in the zone of their external diameter, by crosspieces of small cross-section dimensions.

7. An assembly in accordance with any preceding Claim, wherein the depth to which the slits are cut in the base amounts to about 40% of the diameter of the winding body.

8. An assembly in accordance with any preceding Claim, wherein the slits are offset by 45 angular degrees in relation to one another between the annular sectors of the two switch contacts.

t t 1 1

9. An assembly in accordance with any preceding Claim, wherein each annular sector has two incisions taking their course from the inside to the outside in the radial direction.

10. An assembly in accordance with any preceding Claim, wherein the annular sectors consist of sinter metal having about 75 parts copper and about 25 parts of Chromium.

11. An assembly in accordance with any preceding Claim, wherein the annular sectors are offset in the manner of a step on the external periphery and toroidally bevelled on the radially innermost zone.

12. A vacuum switch chamber assembly substantially as described herein with reference to the accompanying drawings.

Published 1991 at The Patent Office. State House. 66171 High Holborn. London WC1R 41P. Further copies may be obtained from Sales Branch. Unit 6. Nine Mile Polm Cwrnfelinfach, Cross Keys, N-rL NP1 7HZ. Printed by Multiplex techniques lid. St Mary Cray, Kent.